1. Field of the Invention
The present invention relates to a drive unit of an electric motor and a motorized equipment using the drive unit.
2. Description of Related Art
Conventionally, there has been publicly known a motorized equipment used for electric power steering for assisting steering, which is performed by a driver, the motorized equipment integrating an electric motor and a drive unit for driving the electric motor.
In a drive unit described in each of Patent document 1 (JP-A-2003-204654) and 2 (JP-A-2002-345211), large-size electronic components such as power transistors and capacitors are mounted to a metallic substrate attached to a heat sink.
In a drive unit described in Patent document 3 (JP-A-2005-304203), power transistors and capacitors are mounted to a metallic substrate attached to a heat sink. A control board mounted with a microcomputer and the like is provided to be separated from the metallic substrate by a predetermined distance. A large-current wiring busbar (large current substrate 62) mounted with relays, a choke coil and the like is provided between the metallic substrate and the control board.
In a drive unit described in Patent document 4 (JP-A-2004-254359), power transistors are mounted to a metallic substrate attached to a heat sink. A control board is provided to be separated from the metallic board by a predetermined distance. A large current wiring busbar (large current substrate 28) mounted with relays, capacitors and the like is provided between the metallic substrate and the control board.
In the drive unit of each of Patent documents 1 and 2, the power transistors and the capacitors are mounted to the metallic substrate. Accordingly, an area of the metallic substrate is increased as the number of the power transistors increases. Therefore, there is a concern that a body size of the drive unit enlarges.
In the drive unit described in each of Patent documents 3 and 4, the three layers of substrates are formed by the metallic substrate, the large current wiring busbar and the control board. Therefore, there is a concern that a body size of the drive unit enlarges. Moreover, terminals for electrically connecting the metallic substrate and the large current wiring busbar and terminals for electrically connecting the large current wiring busbar and the control board are necessary. Therefore, the number of parts increases and a manufacturing cost increases. Furthermore, spaces for connecting the terminals to the respective substrates by a soldering process and the like are necessary. Therefore, there is a concern that the body size of the drive unit enlarges.